Technique for modifying the coefficient of friction of ink jet media

ABSTRACT

Ink jet media having low coefficients of friction to enable efficient sheet feeding performance and which are compatible with modern inks. In a preferred embodiment, ink jet media include a substrate, a coating including a binder, a pigment, and a low friction substance. The low friction substance, in an emulsified form, is selected from the group consisting of waxes, simple organic polymers, silicone polymers and fluoropolymers. The binder is selected from the group consisting of polyvinylversatate, polyethelene, polyvinyl alcohol, polyvinylpyrrolidone and polyvinylacetate and it comprises between about 5% and about 30%, by weight, of the coating. Preferably, the pigment is alumina or silica. In addition, polyterfluoroethylene latex is utilized as a slip aid. A method of preparing ink jet media includes the steps of providing a substrate and a coating including a binder, as described above. The binder is mixed with a low friction substance, in an emulsified form, selected from the group consisting of waxes, simple organic polymers, silicone polymers and fluoropolymers. The mixture is applied to the substrate and the substrate is dried.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to ink jet media and,more particularly, to techniques for modifying the coefficient offriction of such media.

[0002] The need for coated paper is well established. Paper may becoated with polymeric or wax coatings for various reasons such as forimparting water resistance, increasing strength of paper stock,enhancing gloss and improving barrier qualities.

[0003] The selection of coatings for the paper media utilized in modernimage transfer devices, including ink jet printers, presents severalproblems. For example, because of the necessity that such coatings becapable of absorbing water based inks, the coatings tend to be softenedby water or humidity. As a result, when two of these coatings are incontact, interaction between soft polymer coatings tends to be high andsome sticking results. This factor can present significant problemsfeeding a single sheet from a paper stack to a printer is desired. Inaddition, humidity in some cases can contribute to a tacky feeling inwhich is not aesthetically pleasing to the user and which can make thepaper relatively difficult to handle.

[0004] Many of the pigments utilized in conventional ink jet coatingsare characterized by high coefficients of friction. In fact, the silicaand alumina pigments frequently utilized are referred to as“frictionizers”. Further, since it is often desirable that the mediahave a smooth texture and glossy consistency, the techniques utilized toachieve these characteristics often produce media having highcoefficients of friction.

[0005] As mentioned, media having a high coefficient of friction can betroublesome in sheet feeding printer operations because of the tendencyof one sheet to stick to another. The coefficient of friction problembecomes particularly troublesome when a glossy ink jet coating isdesired on both sides of the media, in order to support two sidedprinting.

[0006] Some prior art solutions to the above described problems havebeen attempted. In U.S. Pat. No. 5,700,582, for example, backingmaterials are placed on a media substrate to reduce electrostatic chargeand to reduce sheet to sheet friction and sticking. While this approachmay have value in some cases, it is not suitable for media intended fortwo sided printing.

[0007] U.S. Pat. No. 5,474,843 discloses the use of polymeric beadssticking through the surface of the media coating to improve sheetfeeding properties. This solution is not compatible with some modernpaper production processes. For example, it is not acceptable in acoating doctoring process to have particulates catch on the doctoringapparatus with scratches thereby produced in the coating. Calendaring orother smoothing processes will also diminish the utility of thistechnique, as the polymeric beads tend to be pushed into the coating.

[0008] From the foregoing it is apparent that there is a need for glossyink jet media coatings that are compatible with modern inks and thathave a low coefficient of friction to enable efficient sheet feedingfunctions.

[0009] Desirably, as an additional benefit, such media coatings wouldhave a non-tacky consistency for good handleability.

SUMMARY OF THE INVENTION

[0010] According to the present invention, there are provided ink jetmedia having low coefficients of friction to enable efficient sheetfeeding performance and which are compatible with modern inks. In apreferred embodiment, ink jet media include a substrate and a coatingincluding a binder, a pigment, and a low friction substance. The lowfriction substance, in an emulsified form, is selected from the groupconsisting of waxes, simple organic polymers, silicone polymers andfluoropolymers. In a preferred embodiment, polyterfluoroethylene latexis utilized as a slip aid. The binder is selected from the groupconsisting of polyvinylversatate, polyethelene, polyvinyl alcohol,polyvinylpyrrolidone and polyvinylacetate and it comprises between about5% and about 30%, by weight, of the coating. Preferably, the pigment isalumina or silica.

[0011] A method of preparing ink jet media of the present inventionincludes the steps of providing a substrate and a coating including abinder, as described above. The binder is mixed with a low frictionsubstance, in an emulsified form, selected from the group consisting ofwaxes, simple organic polymers, silicone polymers and fluoropolymers.The mixture is applied to the substrate and the substrate is dried.

[0012] The present invention affords several advantages overconventional media coating techniques. For example, it utilizes lowfriction materials in an emulsified form to decrease the coefficient offriction of a two-sided ink jet coating. In general, low frictionmaterials may be described as waxes, simple organic polymers, siliconepolymers or fluorinated polymers. The use of these materials in anemulsified form allows easy incorporation into a water-based coating.This technique is novel and original since it is generally believed thatthese materials do not function at high concentrations in an ink jetcoating because of their hydrophobic nature, which suggests poor wettingand adsorptivity of water based inks. In this regard, it has beendiscovered that the use of low-friction materials allows a decrease ofsheet coefficient of friction without degrading image quality.

[0013] In addition, the examples set forth herein support the hypothesisthat the preparation of the coating materials in emulsion form impartsdesirable properties to the media when contacted with ink jet ink.

[0014] Other aspects and advantages of the present invention will becomeapparent from the following detailed description, illustrating by way ofexample the principles of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

[0016] A preferred embodiment of the present invention provides glossyink jet media coatings that are compatible with modern inks and have alow coefficient of friction, to enable efficient sheet feedingfunctions. The inventive technique enables effective and efficienttwo-sided copying wherein both paper sides utilize glossy coatingshaving a low coefficient of friction. In this manner, improved inkretention is achieved while sheet-feeding problems are substantiallyreduced.

[0017] In a preferred embodiment, an ink jet media coating comprises asubstrate including a binder and a low friction, in an emulsified form,selected from the group consisting of waxes, simple organic polymers,silicone polymers and fluoropolymers. Preferably, polyterfluoroethylenelatex is utilized as a slip aid. The binder is selected from the groupconsisting of polyvinylversatate, polyethelene, polyvinyl alcohol,polyvinylpyrrolidone and polyvinylacetate and it comprises between about5% and about 30%, by weight, of the coating.

[0018] A method of preparing ink jet media of the present inventionincludes the steps of providing a substrate and a binder as describedabove. The binder is mixed with a low friction substance, in anemulsified form, selected from the group consisting of waxes, simpleorganic polymers, silicone polymers and fluoropolymers. The mixture isapplied to the substrate and the substrate is dried.

[0019] In the presently preferred embodiment, the slip aid is adispersion in water and preferably, is polymeric. The particle size ofthe dispersion is less than 5 μm, or preferably, less than 1 μm. While avariety of functional groups are feasible, the preferred slip aid mainlyincludes the elements carbon, hydrogen, fluorine, silicon or the “oxo”form of oxygen for maintaining desired friction properties. Theseelements are found in waxes, simple organic polymers, silicone polymersand fluoridated polymers. In general, a number of latex dispersions maybe classified as slip aids. Polyterfluoroethylene latex, available fromE.I. duPont de Nemours and Co. under the trademark Zonyl® TE-3667N, anda high molecular weight polyethylene wax, available from ShamrockTechnologies, Inc., Newark, N.J. under the designation Hydrocer-355,have proven effective. Other suitable slip aids are a nonionicpolyethylene emulsion sold by Air Products and Chemicals, Inc.,Allentown, Pa., as Vancryl® Wax 35 and a carnauba wax produced byMichelman, Inc., Cincinnati, Ohio, under the trademark MICHEM® LUBE 160.

[0020] According to the present invention, an ink jet coating is appliedto a substrate by conventional methods. Typically, the coating includespigment, binder and performance additives. A preferred pigment ispsuedo-boehmite alumina, manufactured by Condea-Vista as Dispal 11N7-80.Its particle size in water is about 0.25 μm while dried particle size isabout 50 μm.

[0021] In a preferred embodiment, the binders are polyvinylversatatepolyethylene, present as a non-water soluble emulsion polymer,polyvinylalcohol and polyvinylpyrrolidone polyvinylacetate copolymer.The latter two are water soluble. These binders are present in dry solidweight percents of 2%, 0.6% and 11%, respectively. Thepolyvinylversatate polyethylene copolymer is manufactured by Mapei, Inc.of Canada, as Vinavil® 3525. The polyvinylalcohol is manufactured by AirProducts and Chemicals, Inc., as Airvol® 165 and polyvinylpyrrolidonepolyvinylacetate copolymer is available from Badische Anilin &Soda-Fabrik Aktiengesellschaft, Germany, under the trademark Luviskol®.

[0022] Performance additives are utilized for several reasons. Forexample, to control bleed and uniformity, diamine ethylene/propyleneoxide surfactant, manufactured by BASF Corp. as Tetronic™ 701 andglycol, manufactured by Aldrich Chemical, are utilized. An organic acid,such as lactic acid manufactured by Aldrich, functions as a performanceadditive to control viscosity and bleeding. A silicon ether surfactant,manufactured by Air Products as Surfonyl™ D-58 serves as a performanceadditive to reduce foam. Finally, the performance additivepolyterfluoroethylene latex, manufactured by E.I. DuPont de Nemours andCo. as Zonyl® TE-3667N, functions as a slip aid.

[0023] TABLE I sets forth the composition of a low cost, glossy ink jetcoating, prepared according to the present invention and having arelatively low coefficient of friction. TABLE I General Chemical ClassParts Percent Boehmite alumina Pigment 100 78.40063 PolyvinylversatateBinder 14.4 11.28969 Polyethylene copolymer Polyvinylalcohol Binder 0.80.627205 Polyvinylpyrrolidone Binder 2.9 2.273618 polyvinylacetatecopolymer Diamine Performance 1.1 0.862407 ethylene/propylene additiveoxide surfactant Glycol Performance 1.3 1.019208 additive Lactic acidPerformance 1 0.784006 additive Silicon ether Performance 0.05 0.0392surfactant Additive Polyterfluoroethylene Slip aid 6 4.7040938 latex

[0024] In order to demonstrate the utility of the present invention, inkjet coatings formulated according to the present invention were tested.The examples that follow illustrate certain specific embodiments of theinvention and describe comparative tests with commercially available inkjet media coatings.

EXAMPLE 1

[0025] A coating was prepared that contained the substances set forth inTABLE I. The materials were mixed together and then coated on aclay-coated base sheet using a mayer rod. The sheet was dried for 5minutes at 100° C. and then calendared until glossy. The constituents ofthe coating of Example I are set forth in TABLE II. TABLE II Parts (DryChemical Manufacturer Grade wgt.) Pigment Condea Vista Dispal 10011N7-80 Polymer ISP PVPVA-7/30 3 Polymer Air Products and Airvol ® 165 1Chemicals, Inc. Polymer Vinavil 3525 15 Plastisizer Aldrich ChemicalGlycerol Reagent 2 Surfactant BASF Corp. Tetronic ™ 701 1 Surfactant AirProducts Surfonyl DF-58 0.05 Acid Aldrich Chemical Lactic Acid Reagent 1Slip-aid E.I DuPont de Nemours Polyterfluoro 6 & Co. ethylene latex

EXAMPLE 2

[0026] A second coating was prepared and a glossy sheet was produced bythe method set forth in Example 1. The second coating was identical tothe Example 1 coating except that 6 parts of Shamrock Hydrocer-355 (waxypolymer) were utilized as a slip aid instead of polyterfluoroethylenelatex (Zonyl® TE-3667).

EXAMPLE 3

[0027] A third coating was prepared and a glossy sheet was produced bythe method set forth in Example 1. The coating utilized in this exampleis conventional. It is similar to the coatings of Examples 1 and 2 butdiffered therefrom by having neither the polyterfluoroethylene latex(Zonyl® TE-3667) of Example 1 nor the Shamrock Hydrocer-355polyfluoroethylene polymer of Example 2.

[0028] Comparative tests were conducted on the coatings produced in theexamples. The results are set forth in TABLE III. TABLE III ResultsExample 1 Example 2 Example 3 60 degree gloss <40% <40% <40% IQ (HP890C) high high high Static CoF 0.50 0.48 0.75 Kinetic CoF 0.35 0.350.77 Printed Static CoF 0.67 0.56 0.76 Printed Kinetic CoF 0.42 0.370.77

[0029] As can be seen from the results set forth in TABLE Ill, the useof the slip aid in Examples 1 and 2 enables the production of a glossysheet having excellent print quality. In addition, the coefficient offriction is substantially reduced in the coatings of Examples 1 and 2,in comparison to the conventional coating of Example 3. As a result, inkjet media having reliable sheet feeding properties are produced. Inaddition, the media do not feel tacky when handled.

[0030] It will be evident that there are additional embodiments andapplications which are not disclosed in the detailed description butwhich clearly fall within the scope of the present invention. Thespecification is, therefore, intended not to be limiting, and the scopeof the invention is to be limited only by the following claims.

What is claimed is:
 1. Ink jet media, comprising: a substrate; a coatingincluding a binder; and a low friction substance, in an emulsified form,wherein said substance is selected from the group consisting of waxes,simple organic polymers, silicone polymers and fluoropolymers.
 2. Theink jet media according to claim 1, wherein said binder is selected fromthe group consisting of polyvinylversatate, polyethelene, polyvinylalcohol, polyvinylpyrrolidone and polyvinylacetate.
 3. The ink jet mediaaccording to claim 2, wherein said binder comprises between about 5% andabout 30%, by weight, of said coating.
 4. The ink jet media according toclaim 1, wherein said coating includes a slip aid composition.
 5. Theink jet media according to claim 4, wherein said slip aid composition ispolyterfluoroethylene latex.
 6. The ink jet media according to claim 5,wherein said polyterfluoroethylene latex comprises between about 0.5%and about 15%, by weight, of said coating.
 7. The ink jet mediaaccording to claim 4, wherein said coating includes a performanceadditive.
 8. The ink jet media according to claim 7, wherein saidperformance additive is selected from the group consisting of diamineethylene oxide, diamine propylene oxide, glycol, organic acid andsilicon ether.
 9. The ink jet media according to claim 8, wherein saidperformance additive comprises between about 0.1% and about 5%, byweight, of said coating.
 10. The ink jet media according to claim 1,wherein said coating includes a pigment.
 11. The ink jet media accordingto claim 10, wherein said coating is selected from the group consistingof alumina and silica.
 12. A method of preparing ink jet media,comprising the steps of: providing a substrate; providing a coatingincluding a binder; selecting a low friction substance, in an emulsifiedform, from the group consisting of waxes, simple organic polymers,silicone polymers and fluoropolymers; mixing together said binder andthe selected low friction substance; and applying the mixture to saidsubstrate.
 13. The method according to claim 12, wherein the binderproviding step includes selecting from the group consisting ofpolyvinylversatate, polyethelene, polyvinyl alcohol,polyvinylpyrrolidone and polyvinylacetate.
 14. The method according toclaim 12, wherein the mixing step includes adding sufficient binder tocomprise between about 5% and about 30%, by weight, of said mixture. 15.The method according to claim 12, further including providing aperformance additive.
 16. The method according to claim 15, wherein saidperformance additive providing step includes providingpolyterfluoroethylene latex.
 17. The method according to claim 16,wherein said polyterfluoroethylene latex providing step includesproviding between about 0.5% and about 15%, by weight, of saidpolyterfluoroethylene latex.
 18. The method according to claim 15,wherein said performance additive providing step includes providing asurfactant.
 19. The method according to claim 15, wherein saidperformance additive providing step includes selecting said additivefrom the group consisting of diamine ethylene oxide, diamine propyleneoxide, glycol, organic acid and silicon ether.
 20. The method accordingto claim 19, wherein said performance additive providing step includesproviding between about 0.1% and about 5%, by weight, of said additive.21. The method according to claim 12, wherein said coating providingstep includes providing a slip aid composition.
 22. The method accordingto claim 21, wherein said providing a slip aid composition step includesproviding polyterfluoroethylene latex.
 23. The method according to claim22, wherein said polyterfluoroethylene latex providing step includesproviding a sufficient amount of polyterfluoroethylene latex to comprisebetween about 0.5% and about 15%, by weight, of said coating.
 24. Themethod according to claim 12, wherein said applying step includesapplying said mixture to one side of said substrate.
 25. The methodaccording to claim 12, wherein said applying step includes applying saidmixture to two sides of said substrate.